Primary structure of rat pancreatic lipase mRNA

Biochemical characterization, cloning and molecular modeling of a digestive lipase from red seabream (Pagrus major): Structural explanation of the interaction deficiency with colipase and lipidic interface

Red seabream digestive lipase (RsDL) was purified from fresh pyloric caeca. Pure RsDL has an apparent molecular mass of 50 kDa. The RsDL is more active on short-chain triacylglycerols (TC₄), and enzymatic activity decreases when medium (TC₈) or long-chain (olive oil) triacylglycerols were used as substrates. The specific activities of RsDL are very weak as compared to those obtained with classical pancreatic lipases. No colipase was detected in the red seabream pyloric caeca. Furthermore, the RsDL was not activated by a mammal colipase. Similar results were reported for annular seabream lipase. In order to explain structurally the discrepancies between sparidae and mammal lipases, genes encoding mature RsDL and five other lipases from sparidae fish species were cloned and sequenced. Phylogenetic studies indicated the closest homology of sparidae lipases to bird pancreatic ones. Structural models were built for annular seabream and RsDL under their closed and open forms using mammal pancreatic lipases as templates. Several differences were noticed when analyzing the amino acids corresponding to those involved in HPL binding to colipase. This is likely to prevent interaction between the fish lipase and the mammalian colipase and may explain the fact that mammalian colipase is not effective in activating sparidae lipases. In addition, several hydrophobic residues, playing a key role in anchoring pancreatic lipase onto the lipid interface, are replaced by polar residues in fish lipases. This might explain the reason why the latter enzymes display weak activity levels when compared to mammalian pancreatic lipases.

Role of the structural domains in the functional properties of pancreatic lipase-related protein 2

Although structurally similar, classic pancreatic lipase (PL) and pancreatic lipase-related protein (PLRP)2, expressed in the pancreas of several species, differ in substrate specificity, sensitivity to bile salts and colipase dependence. In order to investigate the role of the two domains of PLRP2 in the function of the protein, two chimeric proteins were designed by swapping the N and C structural domains between the horse PL (Nc and Cc domains) and the horse PLRP2 (N2 and C2 domains). NcC2 and N2Cc proteins were expressed in insect cells, purified by one-step chromatography, and characterized. NcC2 displays the same specific activity as PL, whereas N2Cc has the same as that PLRP2. In contrast to N2Cc, NcC2 is highly sensitive to interfacial denaturation. The lipolytic activity of both chimeric proteins is inhibited by bile salts and is not restored by colipase. Only N2Cc is found to be a strong inhibitor of PL activity, due to competition for colipase binding. Active site-directed inhibition experiments demonstrate that activation of N2Cc occurs in the presence of bile salt and does not require colipase, as does PLRP2. The inability of PLRP2 to form a high-affinity complex with colipase is only due to the C-terminal domain. Indeed, the N-terminal domain can interact with the colipase. PLRP2 properties such as substrate selectivity, specific activity, bile salt-dependent activation and interfacial stability depend on the nature of the N-terminal domain.

Cloning and molecular modelling of turkey pancreatic lipase: structural explanation of the increased interaction power with lipidic interface

Starting from total pancreatic mRNAs, turkey pancreatic lipase (TPL) cDNA was synthesized by RT-PCR and cloned into the PGEM-T vector. Amino acid sequence of the TPL is compared to that of human pancreatic lipase (HPL). A 3-D structure model of TPL was built using the 3-D structure of HPL as template, given the high amino acid sequence homology between the two lipases. Based on this model, the enhanced interaction power of TPL, as compared to that of HPL, into a phosphatidylcholine monolayer film, could be explained. We concluded that an increase in the exposed hydrophobic residues on the surface of TPL would be responsible for an enhanced interaction with a lipidic interface.

Constitutive expression of human pancreatic lipase-related protein 1 in Pichia pastoris

High-level constitutive expression of the human pancreatic lipase-related protein 1 (HPLRP1) was achieved using the methylotrophic yeast Pichia pastoris. The HPLRP1 cDNA, including its original leader sequence, was subcloned into the pGAPZB vector and further integrated into the genome of P. pastoris X-33 under the control of the glyceraldehyde 3-phosphate dehydrogenase (GAP) constitutive promoter. A major protein with a molecular mass of 50 kDa was found to be secreted into the culture medium and was identified using anti-HPLRP1 polyclonal antibodies as HPLRP1 recombinant protein. The level of expression reached 100-120 mg of HPLRP1 per liter of culture medium after 40 h, as attested by specific and quantitative enzyme-linked immunosorbent assay. A single cation-exchange chromatography sufficed to obtain a highly purified recombinant HPLRP1 after direct batch adsorption onto S-Sepharose of the HPLRP1 present in the culture medium, at pH 5.5. N-terminal sequencing and mass spectrometry analysis were carried out to monitor the production of the mature protein and to confirm that its signal peptide was properly processed.

Biochemical characterization, cloning, and molecular modelling of chicken pancreatic lipase

Chicken pancreatic lipase (CPL) was purified from delipidated pancreas. Pure CPL was obtained after ammonium sulphate fractionation, then DEAE-cellulose, Sephacryl S-200 gel filtration, and FPLC Mono-Q Sepharose columns. The pure lipase is a glycosylated monomer having a molecular mass of about 50kDa. The 23 N-terminal amino acid residues of CPL were sequenced. The sequence is similar to those of avian and mammalian pancreatic lipases. CPL presents the interfacial activation phenomenon tested with tripropionin or vinyl ester. When CPL was inhibited by synthetic detergent (TX-100) or amphipathic protein (BSA), simultaneous addition of bile salts and colipase was required to restore the full CPL activity. In the absence of colipase and bile salts, CPL was unable to hydrolyse tributyrin emulsion. This enzyme can tolerate, more efficiently than HPL, the accumulation of long-chain free fatty acids at the interface when olive oil emulsion was used as substrate in the absence of bile salts and colipase. The CPL activity, under these conditions, was linear whereas that of HPL decreased rapidly. Anti-TPL polyclonal antibodies cross-reacted specifically with CPL. The gene encoding the mature CPL was cloned and sequenced. The deduced amino acid sequence of the mature lipase shows a high degree of homology with the mammalian pancreatic lipases. A 3D structure model of CPL was built using the HPL structure as template. We have concluded that a slight increase in the exposed hydrophobic residues on the surface of CPL, as compared to HPL, could be responsible for a higher tolerance to the presence of long-chain free fatty acids at the lipid/water interface.

Regulation of pancreatic lipase by dietary medium chain triglycerides in the weanling rat

Pancreatic lipase (PL) and its related protein 1 (PLRP1) are regulated by the amount of dietary fat through an apparent transcriptional mechanism. Regulation of PL and PLRP1 by type of fat (chain length and degree of saturation) is less well understood. The aim of this study was to determine whether medium-chain triglycerides regulate PL and PLRP1. For 7 d, weanling (21-d-old) Sprague Dawley male rats were fed diets low (11% of energy), moderate (40% of energy), or high (67% of energy) in trioctanoate/tridecanoate (MCT) or safflower (low fat only) oils. Food consumption decreased as dietary MCT increased, and the consumption of MCT diets was lower than that of the low-safflower (control) diet. Final body weight was similar among rats fed the low- or moderate-MCT or control diets, but was significantly reduced (17%) in those fed the high-MCT diets. PL activity was significantly elevated 53-60% (p < 0.002) in rats fed low and moderate MCT diets, respectively, compared with that of rats fed high-MCT or control diets. PL and PLRP1 mRNA levels were not significantly different among diets, suggesting that chain length regulates PL and PLRP1 translationally or posttranslationally. The beta-hydroxybutyrate plasma concentration was significantly (p < 0.02) higher (85%) in rats consuming low-MCT diet compared with those of rats fed the control diet. MCT at low levels, but not high levels, increase PL activity without changing its mRNA levels.

High expression in adult horse of PLRP2 displaying a low phospholipase activity

The physiological role of the two lipase-related proteins, PLRP1 and PLRP2, still remains obscure although some propositions have been made concerning PLRP2. In this paper, we report the presence of high amounts of PLRP2 in adult horse pancreas whereas no PLRP1 could be detected. As well, a non-parallel expression of PLRP2 and PLRP1 is observed in adult cat and dog, since no PLRP2 could be detected in these two species. In adult ox, neither PLRP2 nor PLRP1 could be found. These findings are in favor of a different regulation of the expression of the genes encoding pancreatic lipase and the related proteins according to the species. The cDNA encoding horse PLRP2 has been cloned and the protein expressed in insect cells. Both native and recombinant PLRP2 display the same catalytic properties. They possess a moderate lipase activity, inhibited by bile salts and not restored by colipase. Interestingly, they differ from PLRP2 from other species by their very low phospholipase activity indicating that PLRP2 could not be considered as a general phospholipase as previously postulated. This work highlights the variability of the properties of PLRP2 and rises the question of the physiological function of this protein in adult according to the species.

Characterization of turkey pancreatic lipase

Turkey pancreatic lipase (TPL) was purified from delipidated pancreases. Pure TPL (glycerol ester hydrolase, EC 3.1.1.3) was obtained after ammonium sulfate fractionation, Sephacryl S-200 gel filtration, anion exchange chromatography (DEAE-Sepharose) and size exclusion column using high performance liquid chromatography system (HPLC). The pure lipase, which is not a glycoprotein, was presented as a monomer having a molecular mass of about 45 kDa. The lipase activity was maximal at pH 8.5 and 37 degrees C. TPL hydrolyses the long chains triacylglycerols more efficiently than the short ones. A specific activity of 4300 U/mg was measured on triolein as substrate at 37 degrees C and at pH 8.5 in the presence of colipase and 4 mM NaTDC. This enzyme presents the interfacial activation when using tripropionin as substrate. TPL was inactivated when the enzyme was incubated at 65 degrees C or at pH less than 5. Natural detergent (NaTDC), synthetic detergent (Tween-20) or amphipatic protein (beta-lactoglobulin A) act as potent inhibitors of TPL activity. To restore the lipase activity inhibited by NaTDC, colipase should be added to the hydrolysis system. When lipase is inhibited by synthetic detergent or protein, simultaneous addition of colipase and NaTDC was required to restore the TPL activity. The first 22 N-terminal amino acid residues were sequenced. This sequence was similar to those of mammal's pancreatic lipases. The biochemical properties of pancreatic lipase isolated from bird are similar to those of mammals.

Pancreatic lipase-related protein 1 (PLRP1) is present in the pancreatic juice of several species

Pancreatic lipase-related protein 1 (PLRP1) was purified from human, canine, porcine and rat pancreatic juices. The four PLRP1s were identified using microsequencing methods after performing gel filtration on Ultrogel AcA-54 followed by chromatography on Heparin-Sepharose cation-exchanger. Polyclonal antibodies specific to human PLRP1 (HPLRP1) were raised in the rabbit using a synthetic decapeptide from HPLRP1. The results of Western blotting analysis showed that these antibodies recognized native HPLRP1 and recombinant HPLRP1 produced by insect cells, and cross-reacted only with rat PLRP1 (RPLRP1). No significant lipolytic activity was observed with native canine PLRP1 and recombinant HPLRP1 on various glycerides, phospholipid and vitamin esters, or on cholesterol esters. It was established for the first time that this protein is secreted in variable amounts by the adult exocrine pancreas of several species.

Human pancreatic lipase: an exposed hydrophobic loop from the C-terminal domain may contribute to interfacial binding

Epitope mapping was performed using four anti-HPL monoclonal antibodies (mAb's 81-23, 146-40, 315-25, and 320-24) directed against human pancreatic lipase (HPL). Three HPL mutants produced in insect cells were tested for this purpose: (i) N-HPL, which consists of only the N-terminal domain of HPL, (ii) HPL(-lid), in which a short loop consisting of 5 amino acid residues replaces the full-length 23-residue lid domain present in HPL, and (iii) N-GPLRP2/C-HPL chimera, a chimeric mutant consisting of the N-terminal domain of the guinea pig pancreatic lipase related protein 2 (GPLRP2) fused to the C-terminal domain of HPL. The C-terminal domain of HPL (C-HPL) was prepared in a pure form after performing chymotryptic digestion of HPL. The mAb 146-40 recognizes HPL, HPL(-lid), and N-HPL but not GPLRP2, N-GPLRP2/C-HPL chimera, or the C-HPL. The antibody mAb 146-40 therefore specifically recognizes the N-terminal domain of HPL, and the epitope recognized does not include the amphiphilic lid. On the other hand, mAb's 81-23, 315-25, and 320-24 react specifically to the C-terminal domain of HPL, since they recognize HPL, HPL(-lid), the N-GPLRP2/C-HPL chimera, and the C-HPL but not N-HPL or GPLRP2. It was further established that these three mAb's recognize the same conformational epitope, the structure of which is stabilized by the N-terminal domain in the presence of SDS at concentrations greater than its critical micellar concentration. This conformational epitope was found to be located in the vicinity of Met 397 and Arg 414. These two residues delineate a highly exposed peptide stretch extending from the HPL C-terminal domain, which includes a hydrophobic surface loop (beta5'). Kinetic studies on the HPL/mAb's complexes showed that the lipase activity was much lower in these complexes than in HPL. The results of the present study suggest for the first time that the beta5' loop from the C-terminal domain may be involved in the interaction of HPL with a lipid/water interface.

Pancreatic lipase-related protein type 1: a double mutation restores a significant lipase activity

Besides the active pancreatic lipase (PL) which plays a major role in dietary fat digestion, the presence of a pancreatic lipase related protein 1 (PLRP1) displaying a very low lipolytic activity has been reported in vertebrates. It has been suggested that the reduced lipolytic activity of PLRP1 results from specific features of the N-terminal domain of the protein. Therefore, based on sequence comparison between PL and PLRP1 and modelling experiments, several residues located in the vicinity of the active site pocket of both enzymes have been mutated. In this paper, we report that, as regards to PL, two substitutions in positions 179 and 181 in PLRP1 account for the very low lipolytic activity of the protein. Indeed, substituting these residues (V179 and A181) in PLRP1 for those found in PL (A179 and P181), restores a significant lipolytic activity for PLRP1.

Alkaline lipase from brain: is it the same enzyme as pancreatic lipase from pancreas?

A new alkaline lipase was detected in rat brain and its properties were compared with those of the well-characterized pancreatic lipase and pancreatic lipase-related protein 2. The activity of the alkaline lipase was determined using trioleoylglycerol emulsion at pH 8.0. Subcellular fractions were prepared from brain homogenates by differential centrifugation. Lipase activities of the cytosolic fraction (the supernatant obtained by differential centrifugation of 100,000g) were stimulated by addition of colipase and bile salts and inhibited by addition of an antibody against rat pancreatic lipase. The partially purified enzyme had an isoelectric point of pH 6.8, which was identical to that found for rat pancreatic lipase. The enzyme had interfacial activation and dependence on colipase in the presence of bile salts. The enzyme had no measurable phospholipase A activity. The band produced by the enzyme on SDS-polyacrylamide gel electrophoresis was identical to that of the rat pancreatic lipase when detected by immunoblotting analysis using an antibody against pancreatic lipase. These results show that pancreatic lipase such as alkaline lipase is in rat brain.

Molecular mechanisms of rat and human pancreatic triglyceride lipases

Dietary fats affect health and disease. The assimilation of dietary fats into the body requires that they be digested by lipases. One lipase, pancreatic triglyceride lipase, is essential for the efficient digestion of dietary fats. Pancreatic triglyceride lipase is the archetype of the lipase gene family that includes two homologues of pancreatic triglyceride lipase, pancreatic lipase-related proteins 1 and 2. In recent years, important advances have been made in delineating the mechanisms of lipolysis. The cDNA sequences encoding pancreatic triglyceride lipase and the related proteins have been described. The tertiary structure of human pancreatic triglyceride lipase has been determined alone and in a complex with colipase, a pancreatic protein required for lipase activity in the duodenum. This structural information has allowed the rational design of site-specific mutants of pancreatic triglyceride lipase. Together with the structural information, these mutants have greatly advanced our understanding of the molecular details governing lipolysis. This review describes these studies, which will eventually provide the background for the rational design of nutrition therapy in patients with pancreatic insufficiency and fat malabsorption.

Cloning and expression in insect cells of two pancreatic lipases and a procolipase from Myocastor coypus

The physiological role of pancreatic lipases has traditionally been assigned solely to triacylglyceride metabolism, while the digestion of phospholipids requires the presence of the pancreatic phospholipase A2, a 14-kDa enzyme unrelated to pancreatic lipases. However, in the guinea pig, it was observed that the pancreatic phospholipase A2 was absent and that a guinea pig pancreatic-lipase-related protein 2 (GPL-RP2) was responsible for phospholipase activity, in contrast to the situation observed in other mammalian species. As the guinea pig is a member of the hystricomorph rodents, it was of interest to investigate if other species within this evolutionary suborder display similar characteristics. The coypu (Myocastor coypus) also a member of the hystricomorph rodents, was chosen for further investigations. The cDNAs encoding two pancreatic lipases and a procolipase from the coypu were cloned, expressed and characterized. One lipase, CoPL-RP2, was identified as belonging to the RP2 subfamily, while the second, CoPL, was found to belong to the classical pancreatic lipase subfamily. Enzymic characterization and sequence data suggest a role for coypu colipase as a specific cofactor for CoPL, while this coypu colipase cannot be an important cofactor for CoPL-RP2 in vivo. Also, the new lipase cDNA sequences were used in a phylogentic analysis to reinvestigate the taxonomical position of the hystricomorph rodents (e.g. coypu and guinea pig) with respect to the myomorph rodents (e.g. rat and mouse).

Rat pancreatic lipase and two related proteins: enzymatic properties and mRNA expression during development

We report the cDNA sequences of rat colipase, rat pancreatic lipase (rPL), and a rat pancreatic lipase-related protein (rPLRP). Comparison to the human PLRP cDNA suggests that the isolated clone encodes rPLRP-2. Both cDNA and a third cDNA encoding rPLRP-1 are secreted from Sf9 cells infected with recombinant baculovirus. rPL and rPLRP-2 hydrolyze triolein, 8.0 and 4.4 mumol.min-1.microgram-1, respectively. They are inhibited by bile salts, and activity is restored by (pro)colipase. PLRP-1 has barely detectable activity against triolein, even with (pro)colipase present. The pattern of mRNA expression during development in the rat reveals that all mRNA are low in the fetal rat pancreas. Both PLRP mRNA rise just before birth to a maximum 12 h after birth. They fall to low levels in the adult. In contrast, the PL mRNA is low at birth and rises rapidly during the suckling-weanling transition. In conclusion, the rat has at least three genes encoding different lipases, and these related genes have separate regulatory controls.

Cloning of the classical guinea pig pancreatic lipase and comparison with the lipase related protein 2

Starting from total pancreatic mRNAs, the classical guinea pig pancreatic lipase was cloned using rapid amplification of 3' and 5' cDNA ends. Internal oligonucleotide primers were designed from a partial cDNA clone including the region coding for the lid domain. Using this strategy, we did not amplify the cDNA corresponding to the pancreatic lipase related protein 2 in which the lid domain is deleted. Amino acid sequences of the classical guinea pig pancreatic lipase and the related protein 2 were compared based on the primary and tertiary structures of the classical human pancreatic lipase. Their distinct physiological roles are discussed in the light of functional amino acid differences.

Cloning, sequence and structural features of a lipase from the antarctic facultative psychrophile Psychrobacter immobilis B10

A lipase gene (lip1) from the facultative psychrophilic strain Psychrobacter immobilis B10 has been cloned and sequenced. The deduced preprotein sequence is composed of 317 amino acids with a predicted M(r) of 35,288. A primary structure alignment of lipases including lip1 shows conserved elements for which a structural role is proposed in the light of recent crystallographic studies. The analysis of the psychrophilic enzyme sequence suggests characteristics in relation with the adaptation to cold.

Molecular cloning and characterization of rabbit pancreatic triglyceride lipase

Pancreatic lipase (triacylglycerol acylhydrolase, EC 3.1.1.3) has been cloned from a gt11 cDNA library made from poly A+ RNA of adult rabbit pancreas. Pancreatic lipase (PL) assists the absorption of dietary triglycerides by hydrolyzing them at 1 and 3 positions to free fatty acids and 2-monoacylglycerol in the presence of bile acids and colipase in the intestinal lumen. Since rabbits are classifically used for the study of the diet induced changes in the lipid metabolism, as a prelude to studying the diet and age dependent changes in the expression of this enzyme, a full length PL cDNA clone was obtained from its pancreas. The coding region of rabbit pancreatic lipase cDNA consists of 1407 base pairs contained in an open reading frame encoding 469 amino acids including the 16 that constitute the signal peptide. Northern blot analysis revealed a band around 1.5 kb. When rabbit enzyme is compared to other species, an over all homology of 70-80% was observed at the nucleotide level. High homology in the amino acid sequence and composition is also apparent between rabbit and other species like dog (65%), pig (76%) and rat (63%). Highest homology is found to be around active-site serine. The regions of homology with other species may help to define sites of interaction of lipase with co-lipase.

Direct involvement of the C-terminal extremity of pancreatic lipase (403-449) in colipase binding

After a selective cleavage of a lipase/colipase cross-linked complex, the colipase has been shown to be bound to a 5 kDa lipase fragment identified as the C-terminal extremity of the chain extending from residue 403 to the C-terminus (Cys 449). The colipase binding site on lipase is therefore localized in a restricted contact area. Moreover, from sequence comparison of lipase from various species, an acidic residue, Glu 440, is likely to be involved in ion pairing with colipase.